anyone the realizes that bias pot has no effect over the bias or the emmiter resistors and keep the amp playing makes a mistake

obviously either there is a problem caused by you or the designer arround the vbe multiplier area or simply you are not measuring a few millivolts and look for much higher voltage in the wrong resistor

you choise about amplifiers is dramatically poor a quasi complementary amplifier with 4 output transitors and each and everyone of them has its own driver will be a nightmare to stabilize if not designed properly

as about the choise of the cheap 150W amplifier all your results are may correct but not enough ....

your testing procedures are not even close to real life conditions and its expected your cheap 150W to only survive just a few minutes before blowing an expensive speaker ..

i will not bother to explain why once more ( Jhon fisher actually is a guy that i like very much ,exchange emails with ... he is a very cheerfull guy , quitar player and music composer ...he has not much to do with electronics and this a circuit given from a friend to a friend as a quick crappy solution . ) ..... obviously if the amplifier is not allready returned to u in a very smoky enclosure ....dont worrie ....it will any minute now ....

the idea is quickly get back the cheap 150w amplifier ....replace it with a working circuit

then since you dont like me any more ( cause of my tone ) ask other forum members to advice you on bias setups and real life resistive /inductive/capacitive tests on amplifiers

......... notice there are no caps on the rails themselves. So I added a 100uF filter and a 0.1uF bypass cap to each rail. .................... There was no parasitic oscillation from zero signal to clipping. Looks like lack of caps was the problem..............don't underestimate the need for on-board filter and bypass capacitors on the rails.

called decoupling.

Absolutely mandatory to meet the fast changing current demands of devices on the PCB.

It might be even better to locate the decoupling caps right across the devices that have this fast changing current demand. 4 output devices = 4 decoupling caps.

__________________
regards Andrew T.
Sent from my desktop computer using a keyboard

The output transistor quiescent current is not monitored.
The bias knob is only having a direct effect upon drivers.
Who knows how hot the outputs will get???
0.22R in the collector circuit is useless.

How to fix:
Cut path from upper driver emitters and lower driver diode par 100R
direct to the load, and rewire these to the output collectors instead.

Now sum of each driver + output current is watched over by 0.22R
Your bias knob will now work properly, and maybe you can
tweak away the parasitic thing....